In many wells, such as oil and gas wells, a submersible pump, such as an electrically operated pump, is requried to pump fluid from the well to the surface. In these wells it has been necessary to utilize a reverse flow check valve in the tubing string above the pump to prevent backflow of the well fluid to the formation when the pump is shut down. Backflow of the production fluid to the formation is generally not desirable as it sometimes results in formation damage. Another reason for the use of the reverse flow check valve is that reverse fluid flow through most electrical submersible pumps results in pump damage. Presently the reverse flow check valves being generally used consist of a ball and seat. However, this type of valve has short life due to the continuous contact of the production flow path with and erosion of the valve ball and seat.
The present invention is directed to the provision of a reverse flow check valve which is dependable, has a long life and one in which reverse flow pump through capabilities can be provided if it is desired to kill the well.